Electric vehicles (EVs) have been actively studied because they are the most promising solution to pollution and energy problems.
Electric vehicles (EVs) are mainly powered by driving an AC or DC motor using battery power. Electric vehicles are broadly classified into battery powered electric vehicles and hybrid electric vehicles. In the battery powered electric vehicles, a motor is driven using power of a battery, and the battery is recharged after stored power is completely consumed. In hybrid electric vehicles, a battery is charged with electricity generated via engine driving, and an electric motor is driven using the electricity to realize vehicle movement.
The hybrid electric vehicles may further be classified into serial type ones and parallel type ones. In the case of serial hybrid electric vehicles, mechanical energy output from an engine is changed into electric energy via a generator, and the electric energy is fed to a battery or motor. Thus, the serial hybrid electric vehicles are always driven by a motor similar to conventional electric vehicles, but an engine and generator are added for the purpose of increasing range. Parallel hybrid electric vehicles may be driven using two power sources, i.e. a battery and an engine (gasoline or diesel). Also, the parallel hybrid electric vehicles may be driven using both the engine and the motor according to traveling conditions.
With recent development of motor/control technologies, small high-output and high-efficiency systems have been developed. By replacing a DC motor with an AC motor, electric vehicles have accomplished considerably enhanced output and power performance (acceleration performance and maximum speed) comparable to those of gasoline vehicles. As a result of promoting a higher output and higher revolutions per minute, a motor has achieved reduction in weight and size, and consequently reduction in the weight and size of a vehicle provided with the motor.
A battery of the electric vehicle is charged with power and the vehicle starts driving using the battery power, such that it is necessary to stably supply the current charged in the battery to the vehicle as soon as the vehicle starts driving.
In order to supply or cut off the current charged in the battery, the electric vehicle includes a plurality of relays serving as a switching unit. If the plurality of relays serving as the switching unit abnormally operates, an unexpected problem may occur in power supply or power cutoff.
Specifically, the relays may be damaged by heat caused by overcurrent such that an unexpected problem may occur in supply of power acting as the principal power source of the electric vehicle. In order to check whether any of the relays is damaged, a user must detach some components from the electric vehicle, resulting in great inconvenience.
Consequently, there is a need to develop a method for enabling the electric vehicle to check a switching state as well as to perform correct switching.